The objective of this proposal is to investigate the tunicate blood cell, and the role of vandium in its function. The studies will be directed towards testing our model of vanadate transport through blood cell membranes and tunicin synthesis by vanadocytes. To understand the mechanism of vanadium accumulation we propose (a) to measure intracellular pH and the transport rate of vanadate and other anions; and (b) to isolate vacuoles and measure their pH and anionic transport rates. The dependence of transport rates on inhibitors and temperature will test whether uptake is active. Tunicin antibodies marked with a fluorescent label will be prepared. Synthesis of tunicin would be stimulated and evidence sought for the binding of anti-tunicin. These studies will better define the function of vanadocytes, and serve as a model for the true function of vandium in human red cells.